Greenhouse gases from deforestation in Brazilian Amazonia: Net committed emissions

Deforestation in Brazilian Amazonia is a significant source of greenhouse gases today and, with almost 90% of the originally forested area still uncleared, is a very large potential source of future emissions. The 1990 rate of loss of forest (13.8 x 10(3) km(2)/year) and cerrado savanna (approximately 5 x 10(3) km(2)/year) was responsible for releasing approximately 261 x 10(6) metric tons of carbon (10(6) t C) in the form of CO2, or 274-285 x 10(6) t of CO2-equivalent C considering IPCC 1994 global warming potentials for trace gases over a 100-year horizon. These calculations consider conversion to a landscape of agriculture, productive pasture, degraded pasture, secondary forest, and regenerated forest in the proportions corresponding to the equilibrium condition implied by current land-use patterns. Emissions are expressed as 'net committed emissions', or the gases released over a period of years as the carbon stock in each hectare deforested approaches a new equilibrium in the landscape that replaces the original forest. For low and high trace gas scenarios, respectively, 1990 clearing produced net committed emissions (in 10(6) t of gas) of 957-958 for CO2, 1.10-1.42 for CH4, 28-35 for CO, 0.06-0.16 for N2O, 0.74-0.74 for NOx and 0.58-1.16 for non-methane hydrocarbons.